diff --git a/libs/algorithm/test/all_of_equal.cpp b/libs/algorithm/test/all_of_equal.cpp
new file mode 100644
index 00000000..7233a536
--- /dev/null
+++ b/libs/algorithm/test/all_of_equal.cpp
@@ -0,0 +1,40 @@
+#ifndef SPROUT_LIBS_ALGORITHM_TEST_ALL_OF_EQUAL_CPP
+#define SPROUT_LIBS_ALGORITHM_TEST_ALL_OF_EQUAL_CPP
+
+#include <sprout/algorithm/all_of_equal.hpp>
+#include <sprout/array.hpp>
+#include <sprout/container.hpp>
+#include <testspr/tools.hpp>
+
+namespace testspr {
+	static void algorithm_all_of_equal_test() {
+		using namespace sprout;
+		{
+			SPROUT_STATIC_CONSTEXPR auto arr1 = array<int, 10>{{1, 1, 1, 1, 1, 10, 10, 10, 10, 10}};
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::all_of_equal(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					1
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::all_of_equal(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					1
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+		}
+	}
+}	// namespace testspr
+
+#ifndef TESTSPR_CPP_INCLUDE
+#	define TESTSPR_TEST_FUNCTION testspr::algorithm_all_of_equal_test
+#	include <testspr/include_main.hpp>
+#endif
+
+#endif	// #ifndef SPROUT_LIBS_ALGORITHM_TEST_ALL_OF_EQUAL_CPP
diff --git a/libs/algorithm/test/any_of_equal.cpp b/libs/algorithm/test/any_of_equal.cpp
new file mode 100644
index 00000000..2026b344
--- /dev/null
+++ b/libs/algorithm/test/any_of_equal.cpp
@@ -0,0 +1,56 @@
+#ifndef SPROUT_LIBS_ALGORITHM_TEST_ANY_OF_EQUAL_CPP
+#define SPROUT_LIBS_ALGORITHM_TEST_ANY_OF_EQUAL_CPP
+
+#include <sprout/algorithm/any_of_equal.hpp>
+#include <sprout/array.hpp>
+#include <sprout/container.hpp>
+#include <testspr/tools.hpp>
+
+namespace testspr {
+	static void algorithm_any_of_equal_test() {
+		using namespace sprout;
+		{
+			SPROUT_STATIC_CONSTEXPR auto arr1 = array<int, 10>{{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}};
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::any_of_equal(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					10
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::any_of_equal(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					11
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::any_of_equal(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					10
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::any_of_equal(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					11
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+		}
+	}
+}	// namespace testspr
+
+#ifndef TESTSPR_CPP_INCLUDE
+#	define TESTSPR_TEST_FUNCTION testspr::algorithm_any_of_equal_test
+#	include <testspr/include_main.hpp>
+#endif
+
+#endif	// #ifndef SPROUT_LIBS_ALGORITHM_TEST_ANY_OF_EQUAL_CPP
diff --git a/libs/algorithm/test/non_modifying.cpp b/libs/algorithm/test/non_modifying.cpp
index 3e95cc59..7ac63545 100644
--- a/libs/algorithm/test/non_modifying.cpp
+++ b/libs/algorithm/test/non_modifying.cpp
@@ -41,6 +41,10 @@
 #include "./max_element.cpp"
 #include "./minmax_element.cpp"
 #include "./lexicographical_compare.cpp"
+#include "./all_of_equal.cpp"
+#include "./any_of_equal.cpp"
+#include "./none_of_equal.cpp"
+#include "./one_of_equal.cpp"
 
 #ifdef TESTSPR_CPP_INCLUDE_DISABLE_SPROUT_LIBS_ALGORITHM_TEST_NON_MODIFYIING_CPP
 #	undef TESTSPR_CPP_INCLUDE
@@ -83,6 +87,10 @@ namespace testspr {
 		testspr::algorithm_max_element_test();
 		testspr::algorithm_minmax_element_test();
 		testspr::algorithm_lexicographical_compare_test();
+		testspr::algorithm_all_of_equal_test();
+		testspr::algorithm_any_of_equal_test();
+		testspr::algorithm_none_of_equal_test();
+		testspr::algorithm_one_of_equal_test();
 	}
 }	// namespace testspr
 
diff --git a/libs/algorithm/test/none_of_equal.cpp b/libs/algorithm/test/none_of_equal.cpp
new file mode 100644
index 00000000..07068150
--- /dev/null
+++ b/libs/algorithm/test/none_of_equal.cpp
@@ -0,0 +1,56 @@
+#ifndef SPROUT_LIBS_ALGORITHM_TEST_NONE_OF_EQUAL_CPP
+#define SPROUT_LIBS_ALGORITHM_TEST_NONE_OF_EQUAL_CPP
+
+#include <sprout/algorithm/none_of_equal.hpp>
+#include <sprout/array.hpp>
+#include <sprout/container.hpp>
+#include <testspr/tools.hpp>
+
+namespace testspr {
+	static void algorithm_none_of_equal_test() {
+		using namespace sprout;
+		{
+			SPROUT_STATIC_CONSTEXPR auto arr1 = array<int, 10>{{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}};
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::none_of_equal(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					10
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::none_of_equal(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					11
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::none_of_equal(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					10
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::none_of_equal(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					11
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+		}
+	}
+}	// namespace testspr
+
+#ifndef TESTSPR_CPP_INCLUDE
+#	define TESTSPR_TEST_FUNCTION testspr::algorithm_none_of_equal_test
+#	include <testspr/include_main.hpp>
+#endif
+
+#endif	// #ifndef SPROUT_LIBS_ALGORITHM_TEST_NONE_OF_EQUAL_CPP
diff --git a/libs/algorithm/test/one_of_equal.cpp b/libs/algorithm/test/one_of_equal.cpp
new file mode 100644
index 00000000..a8479899
--- /dev/null
+++ b/libs/algorithm/test/one_of_equal.cpp
@@ -0,0 +1,56 @@
+#ifndef SPROUT_LIBS_ALGORITHM_TEST_ONE_OF_EQUAL_CPP
+#define SPROUT_LIBS_ALGORITHM_TEST_ONE_OF_EQUAL_CPP
+
+#include <sprout/algorithm/one_of_equal.hpp>
+#include <sprout/array.hpp>
+#include <sprout/container.hpp>
+#include <testspr/tools.hpp>
+
+namespace testspr {
+	static void algorithm_one_of_equal_test() {
+		using namespace sprout;
+		{
+			SPROUT_STATIC_CONSTEXPR auto arr1 = array<int, 10>{{1, 2, 3, 4, 5, 5, 5, 5, 5, 10}};
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::one_of_equal(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					5
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::one_of_equal(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					10
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::one_of_equal(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					5
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::one_of_equal(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					10
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+		}
+	}
+}	// namespace testspr
+
+#ifndef TESTSPR_CPP_INCLUDE
+#	define TESTSPR_TEST_FUNCTION testspr::algorithm_one_of_equal_test
+#	include <testspr/include_main.hpp>
+#endif
+
+#endif	// #ifndef SPROUT_LIBS_ALGORITHM_TEST_ONE_OF_EQUAL_CPP
diff --git a/sprout/algorithm/all_of_equal.hpp b/sprout/algorithm/all_of_equal.hpp
index 79f4e131..2b3b8f14 100644
--- a/sprout/algorithm/all_of_equal.hpp
+++ b/sprout/algorithm/all_of_equal.hpp
@@ -1,19 +1,73 @@
 #ifndef SPROUT_ALGORITHM_ALL_OF_EQUAL_HPP
 #define SPROUT_ALGORITHM_ALL_OF_EQUAL_HPP
 
+#include <iterator>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
+	namespace detail {
+		template<typename RandomAccessIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		all_of_equal_impl_ra(
+			RandomAccessIterator first, RandomAccessIterator last, T const& value,
+			typename std::iterator_traits<RandomAccessIterator>::difference_type pivot
+			)
+		{
+			return pivot == 0 ? *first == value
+				: sprout::detail::all_of_equal_impl_ra(
+					first, sprout::next(first, pivot), value,
+					pivot / 2
+					)
+					&& sprout::detail::all_of_equal_impl_ra(
+						sprout::next(first, pivot), last, value,
+						(NS_SSCRISK_CEL_OR_SPROUT::distance(first, last) - pivot) / 2
+						)
+				;
+		}
+		template<typename RandomAccessIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		all_of_equal(
+			RandomAccessIterator first, RandomAccessIterator last, T const& value,
+			std::random_access_iterator_tag*
+			)
+		{
+			return first == last ? true
+				: sprout::detail::all_of_equal_impl_ra(first, last, value, NS_SSCRISK_CEL_OR_SPROUT::distance(first, last) / 2)
+				;
+		}
+
+		template<typename InputIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		all_of_equal_impl(InputIterator first, InputIterator last, T const& value) {
+			return first == last ? true
+				:  *first == value && sprout::detail::all_of_equal_impl(sprout::next(first), last, value)
+				;
+		}
+		template<typename InputIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		all_of_equal(
+			InputIterator first, InputIterator last, T const& value,
+			void*
+			)
+		{
+			return sprout::detail::all_of_equal_impl(first, last, value);
+		}
+	}	//namespace detail
+
 	//
 	// all_of_equal
 	//
+	//	recursion depth:
+	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		otherwise -> O(N)
+	//
 	template<typename InputIterator, typename T>
 	inline SPROUT_CONSTEXPR bool
 	all_of_equal(InputIterator first, InputIterator last, T const& value) {
-		return first == last ? true
-			: *first == value && sprout::all_of_equal(sprout::next(first), last, value)
-			;
+		typedef typename std::iterator_traits<InputIterator>::iterator_category* category;
+		return sprout::detail::all_of_equal(first, last, value, category());
 	}
 }	// namespace sprout
 
diff --git a/sprout/algorithm/any_of_equal.hpp b/sprout/algorithm/any_of_equal.hpp
index 2bc6e03c..ea73f4e6 100644
--- a/sprout/algorithm/any_of_equal.hpp
+++ b/sprout/algorithm/any_of_equal.hpp
@@ -1,19 +1,73 @@
 #ifndef SPROUT_ALGORITHM_ANY_OF_EQUAL_HPP
 #define SPROUT_ALGORITHM_ANY_OF_EQUAL_HPP
 
+#include <iterator>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
+	namespace detail {
+		template<typename RandomAccessIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		any_of_equal_impl_ra(
+			RandomAccessIterator first, RandomAccessIterator last, T const& value,
+			typename std::iterator_traits<RandomAccessIterator>::difference_type pivot
+			)
+		{
+			return pivot == 0 ? *first == value
+				: sprout::detail::any_of_equal_impl_ra(
+					first, sprout::next(first, pivot), value,
+					pivot / 2
+					)
+					|| sprout::detail::any_of_equal_impl_ra(
+						sprout::next(first, pivot), last, value,
+						(NS_SSCRISK_CEL_OR_SPROUT::distance(first, last) - pivot) / 2
+						)
+				;
+		}
+		template<typename RandomAccessIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		any_of_equal(
+			RandomAccessIterator first, RandomAccessIterator last, T const& value,
+			std::random_access_iterator_tag*
+			)
+		{
+			return first == last ? false
+				: sprout::detail::any_of_equal_impl_ra(first, last, value, NS_SSCRISK_CEL_OR_SPROUT::distance(first, last) / 2)
+				;
+		}
+
+		template<typename InputIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		any_of_equal_impl(InputIterator first, InputIterator last, T const& value) {
+			return first == last ? false
+				: *first == value || sprout::detail::any_of_equal_impl(sprout::next(first), last, value)
+				;
+		}
+		template<typename InputIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		any_of_equal(
+			InputIterator first, InputIterator last, T const& value,
+			void*
+			)
+		{
+			return sprout::detail::any_of_equal_impl(first, last, value);
+		}
+	}	//namespace detail
+
 	//
 	// any_of_equal
 	//
+	//	recursion depth:
+	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		otherwise -> O(N)
+	//
 	template<typename InputIterator, typename T>
 	inline SPROUT_CONSTEXPR bool
 	any_of_equal(InputIterator first, InputIterator last, T const& value) {
-		return first == last ? false
-			: *first == value || sprout::any_of_equal(sprout::next(first), last, value)
-			;
+		typedef typename std::iterator_traits<InputIterator>::iterator_category* category;
+		return sprout::detail::any_of_equal(first, last, value, category());
 	}
 }	// namespace sprout
 
diff --git a/sprout/algorithm/none_of.hpp b/sprout/algorithm/none_of.hpp
index 5abe3dfb..4dbf3a4a 100644
--- a/sprout/algorithm/none_of.hpp
+++ b/sprout/algorithm/none_of.hpp
@@ -1,8 +1,10 @@
 #ifndef SPROUT_ALGORITHM_NONE_OF_HPP
 #define SPROUT_ALGORITHM_NONE_OF_HPP
 
+#include <iterator>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
 	namespace detail {
diff --git a/sprout/algorithm/none_of_equal.hpp b/sprout/algorithm/none_of_equal.hpp
index 36c3b0ef..ac64f67d 100644
--- a/sprout/algorithm/none_of_equal.hpp
+++ b/sprout/algorithm/none_of_equal.hpp
@@ -1,19 +1,73 @@
 #ifndef SPROUT_ALGORITHM_NONE_OF_EQUAL_HPP
 #define SPROUT_ALGORITHM_NONE_OF_EQUAL_HPP
 
+#include <iterator>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
+	namespace detail {
+		template<typename RandomAccessIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		none_of_equal_impl_ra(
+			RandomAccessIterator first, RandomAccessIterator last, T const& value,
+			typename std::iterator_traits<RandomAccessIterator>::difference_type pivot
+			)
+		{
+			return pivot == 0 ? !(*first == value)
+				: sprout::detail::none_of_equal_impl_ra(
+					first, sprout::next(first, pivot), value,
+					pivot / 2
+					)
+					&& sprout::detail::none_of_equal_impl_ra(
+						sprout::next(first, pivot), last, value,
+						(NS_SSCRISK_CEL_OR_SPROUT::distance(first, last) - pivot) / 2
+						)
+				;
+		}
+		template<typename RandomAccessIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		none_of_equal(
+			RandomAccessIterator first, RandomAccessIterator last, T const& value,
+			std::random_access_iterator_tag*
+			)
+		{
+			return first == last ? true
+				: sprout::detail::none_of_equal_impl_ra(first, last, value, NS_SSCRISK_CEL_OR_SPROUT::distance(first, last) / 2)
+				;
+		}
+
+		template<typename InputIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		none_of_equal_impl(InputIterator first, InputIterator last, T const& value) {
+			return first == last ? true
+				: !(*first == value) && sprout::detail::none_of_equal_impl(sprout::next(first), last, value)
+				;
+		}
+		template<typename InputIterator, typename T>
+		inline SPROUT_CONSTEXPR bool
+		none_of_equal(
+			InputIterator first, InputIterator last, T const& value,
+			void*
+			)
+		{
+			return sprout::detail::none_of_equal_impl(first, last, value);
+		}
+	}	//namespace detail
+
 	//
 	// none_of_equal
 	//
+	//	recursion depth:
+	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		otherwise -> O(N)
+	//
 	template<typename InputIterator, typename T>
 	inline SPROUT_CONSTEXPR bool
 	none_of_equal(InputIterator first, InputIterator last, T const& value) {
-		return first == last ? true
-			: !(*first == value) && sprout::none_of_equal(sprout::next(first), last, value)
-			;
+		typedef typename std::iterator_traits<InputIterator>::iterator_category* category;
+		return sprout::detail::none_of_equal(first, last, value, category());
 	}
 }	// namespace sprout
 
diff --git a/sprout/algorithm/one_of_equal.hpp b/sprout/algorithm/one_of_equal.hpp
index 029d00cc..0362fbb1 100644
--- a/sprout/algorithm/one_of_equal.hpp
+++ b/sprout/algorithm/one_of_equal.hpp
@@ -16,9 +16,14 @@ namespace sprout {
 				;
 		}
 	}	// namespace detail
+
 	//
 	// one_of_equal
 	//
+	//	recursion depth:
+	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		otherwise -> O(N)
+	//
 	template<typename InputIterator, typename T>
 	inline SPROUT_CONSTEXPR bool
 	one_of_equal(InputIterator first, InputIterator last, T const& value) {